1. Field of the Invention
This invention relates to an image forming apparatus such as an electrophotographic printer and a copying machine.
2. Description of Related Art
A conventional image forming apparatus has an exposure device expose a surface of a photosensitive drum uniformly charged by a charging device to form an electrostatic latent image thereon and has a developing device develop the electrostatic latent image to form a toner image, and subsequently transfers the toner image onto a medium and fixes the image thereon. Such a conventional image forming apparatus applies a voltage of a polarity opposite to the toner to a developing roller.
The conventional image forming apparatus has a problem that where a voltage of a polarity opposite to the toner is applied to the developing roller and subsequently the applied voltage is switched to a voltage of the same polarity as the toner, the amount of toner attached to the developing roller increases to cause a higher toner potential, and thus, the increased toner adversely moves to the photosensitive drum irrespectively of the electrostatic latent image during printing. The conventional image forming apparatus has a drawback in that the toner having moved to the photosensitive drum further moves to a recording paper to smear the recording paper.